Manometer



Sept 2, 1952 J. R. MORGAN Erm. 2,608,865

MANOMETER Filed May 26, 1948 lNvENToRs "Ack ROBE/vr M0264 NEL so/v ALEM ATTORNEY Patented Sept. 2, 1952 c MANOMETER Jack Robert Morgan, New York, N. Ys; Nelson Eii'gejiie Alemanes Molini ratify;` Mu.,r l;.uii1` Eugene Alexander' Comley, Minneapolis, Minn., assig'nors to the lUnited States of America as represented byfthe- Secretary' ofthe Navy Application May 26, 1948,s'eria1lN0.e1,788

11' claim. (cl. vel-sm W'K'Ifhis invention relates generally to apparatus for` measuringv fluid' pressures. In particulart relates to an improvement' in manometers for measuringy the pressure generated in` a rocket motorv by. the. combustion of`it's propellant charge in-staticring.

' `In testing. rocletY motors under static conditions two operational ci'iaracteristicsY particularly notedN are the v pressures developed inthen rocket motor by the combustion ofr its propellantcharge and the periodof` time for'whi'ch these pressures exist. The record off these pressure-time' values thus obtainedis o f' great importance as an aid to engineers andbal'listics experts Vin determining. the optimumsiae and weight of projectiles to be propelled by the particular' motor tested, as well asin determiningthe effective rangeA and approximate trajectory of the complete rocket projectile assembly.

One knownmethod. off obtaining-v a pressuretime-record of the-static'rirfg'of' rocket motors includes. connecting theA interiori of the motor chamber to a Bourdon tube pressure gauge having a mirror oniitsgfree-end;andzmaking a photographicY record of the movement of a light beam rected the Vmirror as' the? Bourdon tube moves in accordance with changes in pressure.

When the Bourdon tube: isv calibrated against alsorlsnownr to ll thewpipe system between.- the rocket motor and the Bourdon tube with a liquid, such as oil, to"serv'e as`a medium for gas pressuretransmission. A seriousdisadvantage of the method just described is that the pressure transmission system must be hushed after each test to remove bubbles of combustion gases from the oil, and this, in turn, necessitate the repacking of strain gauges with grease after each test when such gauges are used.

It is one of the objects of this invention, therefore, to provide a direct pressure measuring device which will effectively prevent the penetration of the gases of combustion into the liquid pressure transmission system.

It is another object of this invention to pro- ,clearly apparent from the accompanying draw- A Fig. 1 is a longitudinal sectionarview of 'affref'el'fied elir'ib()dirlientv *ofA `the invention. s'lfl'oililg relation lf a. rocket Irl/61761" to 5e l'esfd a'd pressure recordingdevioe.. Y 1 Fig.` `iS acIoSS-Sedldal viw'talell loi'lgflifl :facing 1'. Q .I

Fig. 3 is a cross-sectional. View taken along'lfie l rigs. 4 and 5f are 'iongiiu'diiiai'sectinai' views of the piston arrangement employed inl curinvention. l Y I l Referring now to Figcl' Aitis seenA that the pressure measuring apparatus there depictedl comprises essentially a casingorbod'y l [having an externally talfiread'edY boss: I2- adaptedV to receive thev forward portionofarocket'y motor i3. Barallel' to the axis ofv the bosslLZ is apassagedelineatingV a cylinder I '4) preferably of circular cross-section, having a portion of enlargedr cliameter defining a-chamber l 6k which isintrnally threadedatV Il at -its openiend. Afthreaded plugl l-8 having a centralv boreconstituti-'ng anexit passage,` equal in cross-sectional arcate-'that of Y passage M and threaded into chamber IB' forms apartition between the. latter and; the rocket motor I3. A piston 9fha'vingan enlarged diameter portion 20 is'tted snugly thepassage I4` and chamber |76; as shown, but movablelongitudinally within' the limits of-chamber H5v under the influence o f uidpressurev exerted at.y its ends. Ports 2 I afford communication between chamber la and the atmosphere-- x InA a preferred.4 designl of our manometer'aport 22' connects passage |-4i witha-fluidsupply` line 23 through' the' agencyI of aconventional connector plug Etf threadedA into a tappedreceptacle (undesignated) in the wall of casing H. A Bourdon tube 21 'fitted with a mirror 28 at its free end measures the pressures in supply line 23 and is connected therewith by a pipe 29. A light source 30 is adapted to cast a beam of light upon mirror 28 which, in turn, directs the light beam to a drum camera 3|. Thus, a continuous trace of the light beam may be recorded the characteristics of which will depend upon the movement of the Bourdon tube in response to changes of pressure in supply line 23. A hydraulic pump 32 and a conventional pressure gauge 33 are provided in a branch 25 of line 23 and are used primarily for calibrating the Bourdon gauge 28. `A valve 34 permits closing oit branch 25 of line 23 when the pump 32 and gauge 33 are not in use.

Other hydraulic connections may be made with passage I4 as desired. For example, a strain gauge 36 may be connected to passage Il through a port 31 and secured to the casing II by any conventional means, or a Vent 38 may be provided for the purpose of bleeding air or gases from the hydraulic uid and may be closed by a plug 39. A second passage 40 communicating with the rocket motor I3 is also preferably included in our manometer to permit the use of a safety valve as 4I designed to rupture at any predetermined pressure. An additional receptacle 42 communicating with passage 40 may be provided for an additional gauge as 43.

In operation, the chamber Ill and the line 23 and all its branches are filled with a hydraulic fluid, entrapped air or gases being removed through the vent 3B. At the outset, piston I9 i5 in the position shown in Fig. 4 in Which the `portion of the piston engages the plug I8 restricting any movement of the piston in that direction. In this position, the piston acts as a sealing valve and allows pressure to be built up in the chamber I4 and fluid supply line 23 and itsbranches. Calibration of the Bourdon tube 21 is'then made by compressing the hydraulic uid in line 23 and all its 4branches to a number of diierent pressures the highest of which will exceed that expected to be produced within the rocket motor by combustion of the propellant charge, and recording the deiiections of the Bourdon tube in response to these pressures. True pressures are recorded continuously from the readings of gauge S3 and it is against these values of pressure that the photographic record of Bourdon tube deflection is calibrated.

After the calibration records are made, pressure in the system is relieved at pump 32 and the system permitted to return to atmospheric pres'- sure with piston I! remaining in the position shown in Fig. 4. Valve 34 is now closed.

As the propellant charge in the rocket motor I3 is consumed, tremendous pressures are generated therein and these, acting upon the exposed portion of piston I9, cause the piston to move deeper into passage I4 and into the position shown in Fig.. 5. Since both ends of piston I9 are of equal area, the oil pressure equals the gas pressure in rocket motor I3 at all times. However, both the hydraulic fluid pressure and the gas pressure within the rocket motor will be greater than the pressure in chamber I5 since the latter is maintained at atmospheric pressure by means of the port 2I. Thus, it is readily apparent that any leakage of combustion gases around that portion of piston I9 adjacent the rocket motor will be quickly eliminated from the system through the ports 2| and will not be forced into the liquid in chamber I4, Flushing the hydraulic system of 'illustrative of a presently preferred embodiment of our invention, it is not intended that the scope of the invention be limited thereto but thatV it embrace any modications and changes which fall within the true spirit of the invention, as

covered by the appended claim, occurring to those Vskilled in the art.

We claim: In a manometer comprising a Bourdon tube having a uid therein and means for translating pressure iiexing of said tube into visual indicia, the combination of a body having an end portion adapted to be attached to a vessel whose fluid pressure is to be measured, a chamber in said end portion opening outwardly and having its outer end internally threaded, a passage coaXially aligned with said chamber and extending from `the bottom of the chamber inwardly of the body, means connecting said passage to said Bourdon tube, a plug threadedly engaged in the threaded end portion of said chamber, said plug being spaced from the bottom of said chamber and having a passage therethrough coaxiaily aligned with said rst passage, said passages having equal cross-sectional areas, a piston having end portions slidably mounted in said rst passage and the passage in said plug, respectively, and including an enlarged central portion slidably mounted iny said chamber, the end portion of the piston slidably supported in said plug in operation being exposed to the interior of the vessel and the fluid whose pressure is` to be measured, and means venting said chamber to the atmosphere whereby leakage of the iiuid whose pressure is being meas-V ured into said chamber is vented to the atmosphere and thereby prevented from mixing with uuid in the Bourdon tube.

JACK ROBERT MORGAN.

NELSON EUGENE ALEXANDER.

EUGENE ALEXANDER COMLEY.

REFERENCES CTED The following, references are of record inthe iile oi this patent:

UNITED STATES PATENTS H 

